The wikipedia atricle only cites american sources so that may be something unique to how US unions operate.

Cousins of American style bumping is definitely in employment law in the UK(where it is done by the employer instead of the employees and union). It also exists at least in Germany(sozialauswahl) where employees theoretically who could get chopped are given points to determine who to chop, where seniority is one of the ways to gain points, as well as age, as well as having children.